1. Field of the Invention
The invention relates to indirect heat transfer plate type film evaporators for the concentration of liquids and more particularly to the use of brush assemblies for distributing liquid to heating surfaces and for cleaning the heating surface.
2. Description of the Prior Art
Falling film evaporators and condensers that employ plate type heat exchange elements are known, as shown, for example in U.S. Pat. No. 3,366,158, granted Jan. 30, 1968. A method for making plate type heat exchange elements that comprise pairs of plates sealed together around their peripheries, leaving a zone within the peripheries free to accomodate heating fluid flow, is described in U.S. Pat. No. 3,512,239, granted May 19, 1970.
Artisan Industries, Inc. of Waltham, Mass., and others, supply wiped film evaporators comprising a jacketed cylinder in which film is scraped off the cylinder wall by a metallic knife. Such evaporators are of small capacity and usually operate at very high temperature differentials. Often the product of such wiped film evaporators is a dry powder rather than a liquid condensate.
Such prior art evaporators do not use brushes to serve the dual functions of distributing liquid as film to heating surface and cleaning the heating surface.